Differential thermostat.



W. H. CARRIER.

DIFFERENTIAL THERMOSTAT.

APPLICATION FILED ooT.11, 1907.

Patented Nov. 3, 1908.

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[u venan aT/rf@ Fc le 1 WILLIS H.-OARRIER,`OF BUFFALO,` NEW YORK,AssIeNoR To BUFFALO FORGE COMPANY,

OF BUFFALO, NEW YORK.

DIFFERENTIAL TmnMos'IAT.

Specification of Letters Patent.

Patented Nov. 3, 1908.

Application filed October 11, 1907. Serial No. 396,982.

To-all whom it may concern:

Be it known that I, WILLIS H. CARRIER, a citizen of the United States,residing at Buffalo, in the county nof Erie and State of New York, haveinvented a new and useful Improvement in Differential Thermostats, ofwhich the following isa specification. l"

This invention relates more particularly' to a differential thermostatfor automatically l regulating/'the temperature vof one off-,two

fluids in such manner as to maintain a definite or-predetermined desireddifference in the temperatures of said fluids, or-adefinite relationbetween such temperatures, notwithstanding temperature changes in theother fluid.

The objects of the invention are to produce an efficient and reliabledevice of the character stated and also to so construct the device thatit can. be adjusted to maintain a constant difference in temperaturebetween the two fluids or any predetermined desired schedule ofdifferences corresponding to variations in temperature of one fluid.These objects are attained by the use of two ther- Inostatic elementswhich are insulated from each other and arranged so that one isinfluenced by the temperature Achanges of one zof the fluids and theother by the tempera- 30 ture changes of the other fluid, said elementsbeing so opposed 4that the thermostatic valve or regulatingdeviceoperated thereby shall be controlled only by a difference in`temperature, orl by a certain relation of difference in tem ierature,of the two fluids, and not merely y fluctuations of' temperature in oneor both fiuids. For adjusting the device to o erate in correspondencewith various di erent temperature relations between the two fluids,Imeans are provided for varying the ratio of expansion of one of thethermostatic elements.

The differential thermostat forming the subject of this invention is`primarily intended for use in the automatic system of humidity andtemperature control disclosed in my. application for U. S. LettersPatent filedMay 17, 1907, Serial No. 374,215, for controlling the dewpoint with reference to the room temperature, but the invention is notrestricted to such application. I g

In the accompanying drawings: Figure 1- is a diagrammatic sectional planof altem# perature and humidity regulating apparatus; equipped with adifferentlal thermostafem'- bodying the invention. Fig. 2 is a sectionalelevation of the thermostat. Fi 3 is aseotional plan thereof in line 33, ig. 2. Fig. 4 is a fragmentary sectional elevation thereof, on anenlarged scale,'in line 4 4, Fig. 2. 1 Fig. 5 is an enlar edsectional-elevation of the g thermostatic Va ve. Fig, g-is a transverseysection of the thermostat..

Like letters of reference refer to like'parts Ain the several figures;

A represents 'a room or building in which the condition ofthe air is tobe controlled; B an air trunk or humidifier having inlet vOpenings b brespectively for outside'air and re- 'turn air from. the building, and adischarge opening b2 leading into the building; C C

-dampers controlling the inlet openings b b;

'D a vfan` or device for circulating the air through the trunk orhumidifier anddischarging it into the building; E sprayers or Isothersuitable means for saturating the vair :current withmoisture; and F aneliminator j for removing the free water or moisture from the air.

G represents the dierential thermostat, which, in the apparatusillustrated., is employed for regulating the temperature of the airentering the humidifier to maintain the difference in the temperature'between the saturated air in the humidifier and that in the buildingnecessary to give a ldesired temperature and humidity of the air in thebuilding. The thermostat comprises two eXpansible elements, g g',preferably arranged one concentrically within and insulated from theother 'with one element secured at one end and influenced by thetemperature of one fluid, and the other element attached at one end tothe free end of the first element and influenced by the temperature ofthe other fluid and operatively connected to temperature-controllingmeans for one of said fluids. In the construction shown in the drawingsthe outer element g is screwed at its upper element also passes' throughand has a -screwthreaded engagement with a central hole in the couplingh. Thepitch of the threads on the adjusting' screw I and the innerelement 'vari the effective expansible le wit o g are the same -so thatb'jrl holding the element g from turning andturmng t e adjusting screw Ione way or the other 1t will screw farther into or out of the innerelement g and th thereof ut shifting the element en wise. The upperfreeend ofthe inner element g bears a ainst a lever K which is held onthe end of tlie element by a s ri k or other suitable means. The leveris ulcrumed in thestationa casing H by' pivots k or in any other suitabe manner. APreferably a hollow plug 7c, Fi 4, is fixed in the u per'endof the inner e ement and provide at op osite sides with knife edges onwhich the ever bears. A stem or shaft ljournaled in a suitable bearingin the casing H and extending loosely .through a hole in the lever K,has asquare end loosely engaging in a squai'e hole in the lug 7c, or isotherwise fashioned to turn'the mner element g. vThis shaft steadies thefree end of the innerelement without intercasi roun s an inner flange mon'the coup ing h fering with the free expansion andl contractionthereof, but by hold' vthe adjusting screw I and turning the shaft oneway or the other, the inner element will be -screwed down or upon ltheadjusting rod so as to shift the position of the lever K and require agreater or less expansion or contraction of the element to effect anoperative movement of theleger. An index k3 fixed on the shaft lfacilitates the adjustment of the inner element. n

M represents an annular insulating partition or tube which is arrangedbetween the inner and outer expansible elements and forms an annularchamber around the inner element which communicates at its upper 4endwith the interior of the casing H t rough a hole in the bottom thereof,so that the inner element will be surrounded and influenced by the airor fiuid from the casing H. The insulating artition is preferably madehollow or with ouble walls and filled with suitable non-conduct'material, such as asbestos, to better ins ate the elements from eachother, and it is secured at its up er end to the H while its lower enloosel surso as not to interfere with the free expansion and contractionof the outer element but to preventcommunication between the air orfluids inside and outside of the partition. The outer expansible elementis preferably perforated, as shown, to allow the free entrance of theoutside -air or fluid into the chamber Ibetween the outer element andthe insulating partition, `which air will supple-v ment the partition 1ninsulating the expansible elements from each other. pipe m screwed intoor otherwise attached to the coupling 'h' forms a continuation of the'chamber surrounding the inner-expansiblev element.

l.The operation of the thermostat is as fol- A tube orl lows :V The fanD forces the cool saturated-air' from the humidifier throu h the casingH and tube or partition M o the thermostat. The inner ex ansible elementis therefore influenced by tlle temperature of this air while the outerex ansible element is influenced b the surroun ing air of the apartmentinwhic the thermostat is located. The two thermostat elements preferablyhav the same coefvficient of expansion and conseruently if likechangesof temperature occur in the two separate bodies of air theexpansion or contraction of one element will offset that of the other'element and the position of the lever K will remain unchanged. Thusvsolong as a predetermined difference of temperature exists between thetemperatures of the two fluids, notwithstandin fluctuations in theirtemper'atures, there w1 be no o erative actionof the thermostatic lever.f, however, the temperatures of the two fluids change unequally, or onlyone varies, then the ex-l pansion or contraction of the two thermostaticelements will not be equal and the lever Will be moved one way or theother, more or less, depending upon the conditions, and through theregulating means will raise or lower the temperaturepf one fluid torestablish the required difference of temperature between the twofluids. By operating the'adjusting screw I as explained, the effectivecxpansible length'of the inner thermostat element can be changed asrequired without al-' tering its relation to the lever K, to securevarious constant differences of temperature be- .tween the two fluids,while by adjusting the inner thermostat element by means of the shaftlits relation to the lever K as well vas its effective expansible lengthis altered so that the thermostat operates in accordance with a variableinstead of a constant difference of temperatures between the two fluids.

T e movement of the thermostatlever K can be transmitted by any known orsuitable means for performing the regulating action. In the apparatusshown, the `freeend of the lever bears on the stem of a valve N in achambenin the casing H. This valve is pressed against its seat and itsstem held against the lever K by' a suitable spring n and controls apipe or passage n leadin from a compressed air reservoir n2 to an or'nary diaphragm or device n for operatin the dampers C and C. An escapeduct n* lea s from the valve chamber into the casing and a valve 11,5 onthe lever K is adapted to close the end of this duct. When the leverswings downwardly byrea son of a greater expansion o f the outer than ofthe inner element, it 4will close the exhaust port and open the valve N,whereupon compressed air will fiow from the reservoir n2 to thediaphragm n3, thereby expanding the latter and more or less closm oneand opening the other of the dampers C. If the lever is moved in theopposite direction by a less expansion of the outer than of the innerelement, the valve N will be closed and the eX- haust port opened, whichallows the escape of the air from the diaphragm and effects the oppositemovement of the dampers.

I claim as my invention:

l. The combination of two thermostat elements arranged with one elementsecured at one end and the other element attached to the free end of thefirst element, an insulating artition between said elements forseparating the, mediums influencing said elements, and regulating meanso rated by said second element, substantial y as set forth.

2. The combination of two thermostat elements arranged one within theother with the outer element secured at one end and the innerV elementattached to the free end of the outer element, said outer element beinginfluenced by the temperature of the surround- 'ing medium, an annularinsulating partition between said elements and formlng a chamber aroundthe inner element for a separate medium, and regulatlng means for one ofsaid medlums operated by sald inner element,

substantially as set forth.

3. The combfnation of two thegmostat elements arranged one within theother, a hollow casing to which said outer element is secured at oneend, said inner element being attached to the free end of said outerelement, an annular insulating partition between said elements forming achamber surrounding said inner element which communicates with saidcasing, and a regulating device in said casing operated by said innerelement, substantially as set forth.

4. The combination of two thermostat elements arranged with one elementsecured at one end, an adjustable connection between the other elementand the free end of the first element for regulating the eHective exansible length of said second element wit out affecting its position, aninsulating partition between said elements for separating the mediumsinfluencing said elements, and regulating means operated by said secondelement,

6. The combination of two thermostat elements arranged with one elementsecured at one end, an adjusting screw connecting the other element tothe free end of the first element, said screw having threadedconnections of like pitch with both elements, an ins'ulating partitionbetween said elements for separating the mediums influencing saidelements, and regulating means operated by said second element,substantially as set forth.

7. The combination of two thermostat elements arranged with one elementsecured at one end, an adjusting screw connecting the other element tothe free end of the first element, said screw having threadedconnections of like` pitch' with both elements, additional means foradjusting said second element on said adjusting screw, an insulatingartition between said elements for separatmg the mediums influencingsaid elements,-

and regulating means operated by said second element, substantially asset forth.

8. The combination of a differential thermostat having two elementswhich are separately influenced by different mediums, and meanscontrolled by the differential action of said thermostat elements formaintaining a definite relation between the tem eratures of said' twomediums, substantialy as set forth. i

9. The combination of a humidifier, means for circulating air throughthe same and discharging the humidified air into a building, adifferential thermostat having two elements insulated from each other,one influenced by the humidified air from said humidifier and the otherelement influenced by the air of said building, and means controlled bysaid differential thermostat for regulating the temperature of air insaid humidifier, substantially as set forth.

l0. The combination of a humidifier, means for circulating air throu hthe same and discharging the humidified air into a building, dampers forregulating the proportion of external air and return-air'from saidbuilding entering said humidifier, a differential thermostat having twoelements insulated from each other, one infiuenced by the humidified airfrom said humidifier, and the other element influenced by the air of'said building, and means controlled by said differential thermostat forregulating the position of said dampers, substantially as set forth.

Witness myhand, this 7th day of October,

WILLIS H. CARRIER.

Witnesses:

C. W. PARKER, C. B. HORNBECK.

